Jaz Fresh pointed out that if you used "-r [number]" as was wrongly described

in the man page, curl would send an invalid HTTP Range: header. The correct
way would be to use "-r [number]-" or even "-r -[number]". Starting now,
curl will warn if this is discovered, and automatically append a dash to the
range before passing it to libcurl.

src/main.c

@@ -2097,8 +2097,24 @@ static ParameterError getparameter(char *flag, /* f or -long-flag */
         return err;
       break;
     case 'r':
-      /* byte range requested */
-      GetStr(&config->range, nextarg);
+      /* Specifying a range WITHOUT A DASH will create an illegal HTTP range
+         (and won't actually be range by definition). The man page previously
+         claimed that to be a good way, why this code is added to work-around
+         it. */
+      if(!strchr(nextarg, '-')) {
+        char buffer[32];
+        curl_off_t off;
+        warnf(config,
+              "A specfied range MUST include at least one dash (-). "
+              "Appending one for you!\n");
+        off = curlx_strtoofft(nextarg, NULL, 10);
+        snprintf(buffer, sizeof(buffer), CURL_FORMAT_OFF_T "-", off);
+        GetStr(&config->range, buffer);
+      }
+      else
+        /* byte range requested */
+        GetStr(&config->range, nextarg);
+
       break;
     case 'R':
       /* use remote file's time */